In an Institute of Electrical and Electronics Engineers (IEEE) 802.16e system, a Base Station (BS) allocates resources to a Mobile Station (MS) that has requested a bandwidth using a ranging code through a Code Division Multiple Access (CDMA) allocation Information Element (IE).
Ranging codes are classified into four types according to purpose, i.e., a ranging code for initial ranging, a ranging code for handover ranging, a ranging code for periodic ranging, and a ranging code for bandwidth request. Conventionally, a plurality of ranging codes is generated and classified into four types according to purpose. Thus, the ranging codes have different indexes.
Table 1 illustrates a CDMA allocation IE.
TABLE 1SizeSyntax(bit)NotesCDMA_Allocation_IE( ) {——Duration6—UIUC4UIUC for transmissionRepetition Coding Indication20b00: No repetition coding0b01: Repetition coding of 2 used0b10: Repetition coding of 4 used0b11: Repetition coding of 6 usedFrame Number Index4LSBs of relevant frame numberRanging Code8—Ranging Symbol8—Ranging subchannel7—BW request mandatory11: Yes0: No}——
In Table 1, a duration field indicates the amount of resources, which a BS allocates to an MS by the CDMA allocation IE, in Orthogonal Frequency Division Multiple Access (OFDMA) symbols. A repetition coding indication field indicates a coding rate of data that the MS is to transmit through the allocated resources.
A frame number index indicates a frame in which the MS has transmitted a CDMA code and four Least Significant Bits (LSBs) of a frame number are used as the frame number index.
A ranging code field indicates a CDMA code transmitted by the MS, a ranging symbol field indicates an OFMA symbol through which the MS has transmitted the CDMA code, and a ranging subchannel field indicates a ranging subchannel through which the MS has transmitted the CDMA code.
FIG. 1 illustrates an initial ranging/handover ranging procedure among competition-based random access ranging procedures.
An advanced mobile station (AMS) may transmit a ranging preamble sequence (ranging code) for initial/handover ranging to an advanced base station (ABS) (S101). The ABS may transmit a reception state and a physical layer (PHY) adjustment value (for example, timing, power, frequency, etc) of a ranging code transmitted by each AMS to the AMS through an AAI_RNG-ACK message (S102). When the ABS has normally received a ranging code, the ABS may allocate uplink resources to the AMS through a CDMA allocation A-MAP IE. The AMS may transmit an RNG-REQ message through the allocated resource region (S103). The ABS may transmit an RNG-RSP message to the AMS in response to the RNG-REQ message (S104).
FIG. 2 illustrates a periodic ranging procedure among competition-based random access ranging procedures.
The AMS may transmit a ranging code for periodic ranging to the ABS (S201). The ABS may transmit a reception state and a physical layer adjustment value (for example, timing, power, frequency, etc.) of a ranging code transmitted by each AMS to the AMS through an AAI_RNG-ACK message (S202).
The AMS may perform a bandwidth request ranging procedure for uplink data transmission to the ABS. The bandwidth request procedure may be mainly divided into a 3-step procedure and a 5-step procedure. The bandwidth request may also be simply referred to as a BR.
FIG. 3 illustrates a competition-based 3-step random access uplink bandwidth request procedure.
The AMS may transmit a quick access message including a BR preamble sequence (BR code) and uplink bandwidth request information (for example, a station ID, a BR index indicating a requested bandwidth size, etc.) to the ABS (1). The ABS may transmit reception states of a quick access message and a BR code transmitted by each AMS to the AMS through a BR ACK A-MAP IE (2). When the ABS has normally received the BR code and the quick access message, the ABS may allocate grant information for allocating UL resources to the AMS through a UL basic assignment A-MAP IE (2). This allows the AMS to transmit UL data through the allocated resource region (3).
FIG. 4 illustrates a competition-based 5-step random access uplink bandwidth request procedure. The 5-step bandwidth request (BR) procedure may be mainly divided into a fallback mode and a normal mode.
First, the 5-step BR procedure is described below assuming the fallback mode.
An AMS may transmit a quick access message including uplink bandwidth request information (a station ID, a BR index indicating the size of a requested bandwidth, etc.) to the ABS (1). The fallback mode corresponds to the case in which the ABS has received only the BR code among the BR code and the quick access message transmitted by the AMS, i.e., in which the ABS has not received the quick access message.
The ABS may transmit the reception states of a BR code and a quick access message transmitted by each AMS to the AMS through a BR ACK A-MAP IE (2). When the ABS has normally received only the BR code transmitted by the AMS, the ABS may allocate uplink resources, which allow the AMS to transmit a BW-REQ message (a BR header), to the AMS through a CDMA allocation A-MAP (2).
The AMS may transmit a BW-REQ message (in the form of a header) to the ABS through the allocated resource region (3). When the ABS has received the BW-REQ message transmitted by the AMS, the ABS may allocate uplink resources to the AMS through a UL basic assignment A-MAP IE (4). The AMS may transmit data to the ABS through the allocated uplink resource region (5).
An overall procedure of the general 5-step BR procedure is similar to the fallback mode with the only difference being that the AMS does not transmit a quick access message at the first step.
In the procedure described above with reference to FIGS. 3 and 4, the AMS may start a BR timer after transmitting a BR code and may transmit data through an allocated resource region upon receiving an uplink grant from the ABS and then may terminate the BR timer. The AMS may request uplink resources from the ABS if an uplink grant is not received from the ABS before the timer expires.
When the ABS has received only the BR code, the ABS allocates uplink resources for BR header transmission to the AMS through a CDMA allocation IE and, when the ABS has also received a BR header or a quick access message, the ABS may allocate uplink resources to the AMS in a unicast manner through a station ID (STID).
In the IEEE 802.16e system, a bandwidth request message is transmitted through a signaling header which has a format described below.
FIG. 5 illustrates a signaling header format used in the IEEE 802.16e system.
In the case in which a Medium Access Control (MAC) header format as shown in FIG. 5 is used in the IEEE 802.16e system, payload is not transmitted subsequent to the MAC header. A type field in the signaling header shown in FIG. 5 may be 3 bits long and may indicate 8 types as illustrated in the following Table 2.
TABLE 2Type field (3 bits)MAC header type (with HT/EC = 0b10)000BR incremental001BR aggregate010PHY channel report011BR with UL Tx power report100BR and CINR report101BR with UL sleep control110SN Report111CQICH allocation request
As shown in Table 2, a BR-REQ message may be transmitted alone and may also be transmitted together with Tx power, CINR, or UL sleep control information.
FIGS. 6 and 7 illustrate a BR signaling header format used in the IEEE 802.16e system.
In FIGS. 6 and 7, a BR field indicates the size of an uplink bandwidth required by an AMS in bytes. The BR may be performed regardless of physical layer modulation and coding. The BR corresponds to each respective Connection ID (CID). Through the BR, it is possible to request a size of 0 to 524,287 bytes when the length of the BR field is 19 bits and to request a size of 0 to 2,047 bytes when the length of the BR field is 11 bits.
In FIGS. 6 and 7, the CID field includes a connection identification having a length of 16 bits indicating which service flow of which AMS corresponds to the header.